BZOJ2118: 墨墨的等式(最短路 数论)

#include<cstdio>
#include<algorithm>
#include<stack>
#include<queue>
#include<cmath>
#include<cstring>
#define lb(x) (x & (-x))
#define Pair pair<int, int> 
#define fi first
#define se second
#define MP(x, y) make_pair(x, y)
#define LL long long 
using namespace std;
const int MAXN = 1e6 + 10;
inline LL read() {
    char c = getchar(); LL x = 0, f = 1;
    while(c < '0' || c > '9') {if(c == '-') f = -1; c = getchar();}
    while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar(); 
    return x * f;
}
int N, vis[MAXN];
LL dis[MAXN], a[MAXN], Mi = 1e15, Bmin, Bmax;
void SPFA() {
    queue<int> q;
    memset(dis, 0xf, sizeof(dis));
    dis[0] = 0; vis[0] = 1, q.push(0);
    while(!q.empty()) {
        int p = q.front(); q.pop(); vis[p] = 1;
        for(int i = 1; i <= N; i++) {
            int to = (p + a[i]) % Mi;//tag
            if(dis[to] > dis[p] + a[i]) {
                dis[to] = dis[p] + a[i];
                if(!vis[to]) vis[to] = 1, q.push(to);
            }
        }
    }
}
LL Query(LL x) {
    LL rt = 0;
    for(int i = 0; i < Mi; i++) 
        if(dis[i] <= x) 
            rt += (x - dis[i]) / Mi + 1;
    return rt;
}
int main() {
    N = read(); Bmin = read(); Bmax = read();
    for(int i = 1; i <= N; i++) {
        a[i] = read();
        if(a[i] != 0) Mi = min(Mi, a[i]);
    }
    SPFA();
    printf("%lld", Query(Bmax) - Query(Bmin - 1));
    return 0;
}
/*

*/